So far, units such as electric and\or electronic bays are classically arranged vertically and integrated in the hold, under the cockpit, but partially extend in the freight area situated under the space for the passenger cabin. The terms “vertical”, “horizontal”, “upper”, “lower”, as well as their derivatives, refer to generally used standard positions in reference to the universal gravity.
These units are classically arranged vertically and are composed on the basis of a load bearing frame including at least two posts on which horizontal shelves are mounted. Shelves and posts are arranged into hermetic boxes with simple or double compartment. These boxes fulfil a structural function as well as a function of integrated air circulation.
Shelves are used to support the electronic modules (computers, cards, additional discs, electronic equipments, power modules, etc.) via standardized intermediate racks. These racks fulfil both the mechanical linkage and the electric connection of every module accommodated in the rack.
On the rear face of the unit, an intermediate electricity network fulfils for every module, or every interconnection between several modules, the connection with the outside electricity network (known as “plane electricity network”) via cutoff plates.
On the front face, an easy access to computers is provided for a quick integration or replacement after a defective function was detected during a phase of maintenance or pre-flight control.
The vertical position of the units facilitates front face and rear face access.
In a more recent standard of integration taking the form of a “cabinet”, a single rack, known as “maxi rack”, occupies a whole shelf. The rear electrical integration is then simplified because all the electrical connectors are arranged on the same mother-board, which is integrated into the cabinet. In this cabinet, the electrical functions are distributed by “blade”-type cards (i.e. relatively low thickness cards). Cabinets are grouped together in a box or arranged individually like the shelves.
As electronic modules dissipate heat and are sensitive to high temperatures as well as to variations in temperature, it is advantageous to ventilate them. To this end, each module is classically cooled by blowing fresh air through the module and then extracting the warm air over every module. The unit is interconnected to the general ventilation circuit of the aircraft.
In order to optimize the available space and thus increase the number of modules, it is well known how to integrate the cooling circuit directly into the frame of the unit to fulfil a thermic exchange with the air circulating in the box. So, as shown by the sectional view of a shelf G according to FIG. 1, a duct for blowing air S and a duct for extracting air E provided in a post M of shelf G—located between two compartments C1 and C2 for housing computers—allow a thermic exchange of air.
Besides, units are generally attached to the structure of the aircraft by means of links made of (Chappe-type) pin and connecting rod. An isostatic global connection is thus obtained with respect to the aircraft structure, which allows to take the deformations of the aircraft structure into account.
However, one seeks at present to install the electric and\or electronic bays in secure spaces because these bays, which integrate more and more all the command and control functions, are of a vital importance. An appropriate secure space would be in particular the cockpit of the aircraft.
The integration of such units in a cockpit was not possible until now because of the clutter problems involved by such an installation, substantially not compatible with the ventilation of avionics bays or units including electronic circuits.